1. Field of the Invention
This invention relates generally to a method of wafer reclaim, further relates to a method for cleaning wafer and a method for planarizing wafer.
2. Description of the Prior Art
In practical semiconductor fabrication, owing to numerous processing steps are performed before a wafer is changed into numerous integrated circuits, the wafer will be failed whenever any processing step is out of order such that actual action on the wafer is different from the predetermined action. Thus, in practical semiconductor fabrication, after parameter(s) of any processing step is set up, in most of case, monitor wafer is processed by the processing step to examine whether the set sup parameter(s) is proper. Then, practical wafers are processed by the tested processing process only while the actual action on the monitor is equal to the predetermined action which decided by the set up parameter(s). For example, before depositing process is performed, in order to ensure thickness and uniformity of deposited film match the desired limitation and pollution induced by particles which are formed during perform of depositing process is acceptable, depositing process is performed to form film on monitor wafer to ensure all requirements and then depositing process is performed to form file(s) on practical wafers when all requirements is satisfied.
Because that cost of each monitor wafer is not low, monitor wafer(s) is repeatedly used in practical semiconductor fabrication to reduce total cost. In other words, after each application, condition of used monitor wafer must be restored to the original condition before monitor wafer is used, to ensure monitor wafer is tested in different cases with same condition. For conventional technologies, after monitor wafer is used, etching process, such as wet etching process, is used to remove action and result, such as film, of monitor processing process and then surface of monitor wafer is cleaned by a cleaning process.
However, conventional technologies do not always can thoroughly restore original condition of monitor wafer. As FIG. 1A shows, some processing processes form both thin film 11 and random distributing particles 12 on monitor wafer 10, where particles 12 usually are by-products of tested processing process and thin film 11 may be not uniform. Obviously, after etching process is completed, the existence of particles 12 as well as the even roughness of thin film 11 and by-product of etching process will induce the existence of residual particles 13, as FIG. 1B show. Thus, because plural available sources of residual particles 13 let residual particles 13 have plural materials, also because cleaning process usually aims at pollution, small particle, and by-products of etching process, cleaning process usually can not thoroughly remove all residual particles 13 and then some defects 14 will appear on surface of monitor wafer 10 after the reclaim process, as FIG. 1C shows, wherein defects 14 is not appeared on the original condition of monitor wafer 10. Certainly, some of the defects 14 perhaps are effectively removed by increasing period of cleaning process or modifying reactant(s) of cleaning process, but disadvantages such as increased cost and decreased efficiency are unavoidable. Without question, defects 14 will induce error messages whenever monitor wafer 10 is used to monitor any processing step again. FIG. 1D shows that thin film 11 and particles 12 are formed on normal monitor wafer 10 without defect, FIG. 1E shows that thin film 11 and particles 12 are formed on monitor wafer 10 with existence of defects 14. By comparing FIG. 1D with FIG. 1E, it is clear that particle-like structure, which usually called as pseudo particle 15, will appear over defect 14 whenever evenness of thin film 11 is affected by existence of defects 14. Significantly, if scale of any pseudo particle 15 is larger than lower limitation of detectable scale of testing process which is used to detect particles on monitor wafer 10, counted number of particles of FIG. 1D is different from counted number of particles of FIG. 1E, and the difference is not induced by error of testing process but is induced by abnormal qualify of monitor wafer 10. Therefore, existence of pseudo particles 10 will let reclaimed monitor wafer(s) 10 can not properly used for process monitoring.
Accordingly, because conventional technologies can not ensure monitor wafer is properly restored after each application, and because existence of defects on monitor wafer will be amplified and induce existence of pseudo particles, it is desired to develop a method for reducing or totally eliminate effect of pseudo particles.
One main object of the invention is to reduce or even eliminate the effect of pseudo particles during wafer reclaim, such as monitor wafer.
Another object of the invention is to present a method for cleaning wafer. Where numerous particles usually exist on surface of wafer or covered by deposition film.
Still an essential object of the invention is to present a method for planarizing wafer, wherein the method uses both chemical mechanical polishing and wet etching.
Further, another main object of the invention is to present a method for effectively removing all residuals of performed process, such as particles, residual particles and defects, with the advantage of simple processing conditions.
Yet a main object of the invention is to present a method of wafer reclaim with the advantages of both low cost and high efficiencies, especially is to present a method for different kind of film removed.
According to previous objects, this invention present a method of wafer reclaim, the method at least includes following steps: provide a wafer; perform a first semiconductor process to let both a thin film layer and numerous particles are formed on the wafer; perform a chemical mechanical polishing process to let part of the thin film layer is removed and most part of the particles are planarized; perform a wet etching process to further remove both residual thin film layer and residual particles; perform a cleaning process to clean surface of wafer; and perform second semiconductor process to let a semiconductor structure is formed on wafer. Where, particles usually are by-products of first semiconductor process and it is hard to remove particles by wet etching process or cleaning process, and particles usually are not thoroughly covered by thin film layer. Furthermore, concepts of the invention that both deposition film layer and particles can be thoroughly removed by both chemical mechanical polishing process and wet etching process, which therefore can be applied as a method for cleaning wafer and a method for removing particles.